This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
Radio-frequency (RF) transmission is widely used in systems such as radar, sensing, wireless communications, and electronic warfare. However, many RF applications are required to cope with noise, multipath dispersion and interference with other RF signal(s). For example, ultra-wideband (UWB) systems operate in a wide frequency band, e.g., 3.1-10.6 GHz. Over this range, signals propagate through and around obstacles by various paths, and those paths can be frequency-dependent. Accordingly, multi-path interference can affect many UWB systems and limit their performance severely.
To combat this type of interference, different pre-equalizers such as Time Reversal (TR) or Minimum Mean Square Error (MMSE) have been proposed, each with its own drawbacks. For example, TR pre-filtering (i.e., pre-equalizing) modifies the transmitted signal based on characteristics of the channel between the transmitter (Tx) and the receiver (Rx) so that the received signal will exhibit reduced corruption compared to a non-pre-filtered transmission. Although TR is computationally simple and maximizes the power in the central peak, it shows a poor performance in sidelobe suppression which becomes important in different applications including high-speed communications. TR signals, when received, include excessive sidelobes that can increase the bit-error rate (BER) of the system due to intersymbol interference (ISI). These sidelobes cannot be significantly suppressed using a TR-based system. There is a limit, therefore, to BER improvement that TR can attain for a given bit rate, and increasing signal-to-noise ratio (SNR) cannot improve the BER performance any further. The MMSE equalizers provide a superior multipath suppression performance compared to TR, but their main drawback is the high implementation complexity (with complexity O(N3) where N is the number of channel taps) which becomes practically important in ultrabroadband systems with large number of tabs.
There is, therefore an unmet need for a novel approach for both line of sight and non-line of sight applications in multipath systems that suffer from high BER and ISI.